Introductory Retrospective The Neal Amundson Era. Rapid Evolution of Chemical Engineering Science Doraiswami Ramkrishna School of Chemical Engineering, Purdue University, West Lafayette, IN 47907 DOI 10.1002/aic.14191 Published online August 5, 2013 in Wiley Online Library (wileyonlinelibrary.com) Neal Amundson (1916–2011) influenced the chemical engineering profession more profoundly than any other single individual, and in this article the author has attempted to capture the man and his era, as well as his lasting legacy. His influence extended well beyond those of other chemical engineers of renown, whether they were known for exploring and establishing new avenues, or for the resolution of outstanding issues, or for other forms of creative endeavors. Amundson reached into the depths of the profession, noted for its expanse, complexity and diversity that had led earlier efforts into a shrine of empiricism, to foster a culture of strongly scientific thinking with a mathematical edifice, which must be the crux of all engineering. The growth of chemical engineering science owes most significantly to Amundson’s extraordinary role as an educator, department head and leader, and to the lasting impact of his contributions to chemi- cal engineering research and practice. This article is in salutation of the man who came to be known as the Minnesota Chief, and was responsible for an academic movement that raised the intellectual level of the chemical engineering pro- fession. VC 2013 American Institute of Chemical Engineers AIChE J, 59: 3147-3157, 2013 Keywords: amundson, chemical engineering science Introduction The arrival of Neal Russell Amundson into the chemical engineering scene must be regarded as heralding his deliberate Olaf A. Hougen once challenged the author of this article effort to build the scientific base of chemical engineering. to produce an equation in a book out of which he had taught Mathematics was indeed to play a key role in this process but, chemical engineering in the 1920s. His challenge was of in his leadership role, it was a quest for the import of basic course prompted by the book’s scrupulous freedom from concepts of all science. This was not simply to be a paradigm equations! As an outgrowth of an engineering profession for shift, but a major cultural change. It deeply involved the crea- the production of chemicals, chemical engineering had its tion of model images of systems; penetrate them to their patho- beginnings in dissecting chemical processes into unit proc- logical limits with mathematical tools, and eliciting guidance esses and unit operations. Unit processes were concerned for experimentation in search of more complete understanding. with the nature of chemical transformations while unit opera- The department he built at Minnesota was a reflection of this tions focused on physical processes of separation, mixing, philosophy. It is the objective of this article to reflect on the and so on. The underlying methodology was largely empiri- Neal Amundson era and the evolution of chemical engineering cal with performance described by correlations linking inde- science during this period. In so doing, we will deliberate not pendent dimensionless groups of the system. The prevailing only on Amundson’s contributions and their impact, but also view of the early chemical engineer was that of a mechani- on his overall influence on the chemical engineering profession. cal engineer, who focused on the manufacture of chemicals. The introduction of material and energy balances by Lewis and Radasch1 andHougenandWatson,2 was a significant Educational Background and Early development in this growth phase of the chemical engineering Academic Days profession. It sowed the seeds of rationally thinking about sys- tems and analyzing them with conservation and thermody- Amundson obtained his Bachelor’s degree in chemical namic principles. It was a precursor to the more microscopic engineering from the University of Minnesota in 1937, and view that followed with the institution of transport phenomena joined Standard Oil Co. (now ExxonMobil) in Baton Rouge by Bird et al.3 which laid the foundation for unifying the as a Process Control Engineer. Neal did not recall the expe- apparent diversity of unit operations and unit processes. rience as particularly interesting, because engineers were denied access to the company’s R&D facilities where the flu- idized catalytic cracker was in its early development. There Correspondence concerning this article should be addressed to D. Ramkrishna at were too many “nonproductive” activities that consumed his [email protected]. energy of which he had ”had enough” by the end of 2 years, VC 2013 American Institute of Chemical Engineers and he returned to the University of Minnesota for graduate AIChE Journal September 2013 Vol. 59, No. 9 3147 studies. He enrolled for a Master’s degree in chemical engi- time was ripe for this activity to flourish. Also Neal had neering there. The Dept. of Chemical Engineering, at that noticed that chemical engineers were not familiar with matri- time housed in the chemistry building, was relatively young ces and introduced them in his courses. The application of but “competent” as Neal described it. He observed, however, matrices could not have had a better beginning than through that the research in the department was “mostly experimental the arrival of Andreas Acrivos as a graduate student on the and dull.” Interestingly, Amundson received his Master’s scene, who subsequently grew to be one of the most distin- degree in chemical engineering in 1941 with the first ever guished academicians of chemical engineering. With Neal’s nonexperimental thesis! research contributions to be discussed later in this article, we There had been “very little mathematics” taught during his turn to other aspects of his academic career. undergraduate days at Minnesota so that Neal’s interest in Following Doc Mann’s unfortunate death in 1949, Neal mathematics was not aroused until after his bachelor’s degree. became the Acting Head of the department, while an exter- Curiously, while he was at Standard Oil, he and a few of his nal search was initiated by Dean Spilhaus for a new Head. colleagues attended evening classes at LSU on differential After some unsuccessful attempts, it was clear that someone equations taught by a Norman Rutt, whom Amundson fondly within the department should take over as Head. Edgar Piret, recalled as a very “charming fellow”! This seems to have a senior colleague of Neal was a potential candidate, but had sowed the seeds of his subsequent involvement with mathe- been rejected by the faculty. Any residual inkling that Dean matics. One wonders whether such excursions are at all a part Spilhaus may have had in offering the Headship to Piret, of students taking courses during graduate work today! was eradicated after his encounter with Neal on the issue. The years that followed were highly consequential for Thus, began the stellar academic career of Neal Amundson, Neal. In light of finding little mathematics in the Chemical a full Professor at age 35, and Head of the Dept. of Chemi- Engineering Dept., he switched to a PhD in mathematics cal Engineering at Minnesota in 1951. under the supervision of Hugh Turrittin at the University of Minnesota. A student of Rudolph Langer of Wisconsin, Tur- As Department Head rittin’s lineage stretched two generations back to the famous Amundson went about building his department with admi- American mathematician, G. D. Birkhoff. The final year of rable support from Dean Spilhaus, who discovered early that Neal’s doctoral thesis was spent at Brown University where Amundson thrived when he was otherwise left alone. his advisor was on sabbatical leave. This could well have Resources were scant at the University for building a strong been the defining period of Neal’s career, for he experienced research program. The focus had to be on hiring theoreti- at Brown an extraordinary atmosphere of mathematics that cians but perhaps also partially out of conviction that the he felt as if had “pulled him out of the water”! He returned profession needed theory at its stage of development. Chemi- to Minnesota in 1945 with a PhD in mathematics, euphoric cal engineering theoreticians were an undefined community about his experience at Brown in the company of eminent so that they had to be sought from other disciplines. Amund- mathematicians, and ideas that perhaps molded his own aca- son was not interested in hiring chemical engineers who pro- demic contributions the most. His doctoral dissertation bore fessed interest in conventional areas like heat and mass the title “Solution of a Nonlinear Partial Differential Equa- transfer. They had to be involved in arresting new directions tion of the Parabolic Type.” in depth. Bill Ranz, whom he hired with a PhD from the Neal began his academic career at the University of Min- University of Wisconsin, came as close to traditional ChE as nesota as an Assistant Professor of Mathematics. Even as a possible, but he certainly was an unusual thinker. His highly young, junior faculty member, his instinct for leadership had cited work on packed beds with Bob Marshall of Wisconsin begun to surface, for he had played an active role in chang- had won him the AIChE Colburn award in 1955. ing the face of Minnesota mathematics by initiating the The story of Amundson’s discovery of Rutherford Aris, move of an eminent mathematician by the name Stephen has often been told but bears repetition because it is an Warschawski from Brown University to head the Dept. of extraordinary one. While a Fulbright Scholar at Cambridge Mathematics at Minnesota. With Warschawski’s arrival, University in 1954/55, Amundson had the opportunity to many new courses were instituted, a full year of partial dif- visit ICI (Imperial Chemical Industries). There in their ferential equations to note in particular.